Question 1

How do I set up OmniAuth with Rails?

Accepted Answer

Add the 'omniauth' and 'omniauth-rails_csrf_protection' gems, create an initializer to configure providers (e.g., in config/initializers/omniauth.rb), define routes for callbacks, and implement a controller to handle the authentication hash from request.env['omniauth.auth']. The README provides a detailed example with code snippets.

Question 2

OmniAuth vs Devise: which is better for my app?

Accepted Answer

OmniAuth is a flexible library for multi-provider authentication that requires manual user management, while Devise is a full-featured authentication solution that integrates OmniAuth with user models out-of-the-box. Choose OmniAuth if you need custom control or multiple providers without Devise's conventions; use Devise for a complete, opinionated system with less coding.

Question 3

How to handle user sessions after OmniAuth authentication?

Accepted Answer

After OmniAuth sets the authentication hash in the Rack environment on the callback request, you must create or find a user in your database based on the data (like uid and info), set up session variables (e.g., using Rails sessions), and redirect appropriately. OmniAuth does not manage sessions, so this is implemented in your callback endpoint.

Question 4

Can I use multiple authentication providers with OmniAuth?

Accepted Answer

Yes, OmniAuth is designed for multi-provider authentication. Configure multiple strategies in the OmniAuth::Builder block, and users can authenticate via different providers, with each callback providing a standardized authentication hash. The built-in Developer strategy can be used alongside others for testing.

Question 5

What data does OmniAuth provide after authentication?

Accepted Answer

OmniAuth sets an authentication hash (request.env['omniauth.auth']) containing user details like a unique id, provider name, and personal info (e.g., name, email) as available from the strategy. Refer to the Auth Hash Schema wiki page for specifics on the hash structure and common fields.

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